netdev - [net-next PATCH 0/3] net: optimize ICMP-reply code path

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Date:   Mon, 09 Jan 2017 16:03:59 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     xiyou.wangcong@...il.com
Subject: [net-next PATCH 0/3] net: optimize ICMP-reply code path

This patchset is optimizing the ICMP-reply code path, for ICMP packets
that gets rate limited. A remote party can easily trigger this code
path by sending packets to port number with no listening service.

Generally the patchset moves the sysctl_icmp_msgs_per_sec ratelimit
checking to earlier in the code path and removes an allocation.

Use-case: The specific case I experienced this being a bottleneck is,
sending UDP packets to a port with no listener, which obviously result
in kernel replying with ICMP Destination Unreachable (type:3), Port
Unreachable (code:3), which cause the bottleneck.

 After Eric and Paolo optimized the UDP socket code, the kernels PPS
processing capabilities is lower for no-listen ports, than normal UDP
sockets.  This is bad for capacity planning when restarting a service.

UDP no-listen benchmark 8xCPUs using pktgen_sample04_many_flows.sh:
 Baseline: 6.6 Mpps
 Patch:   14.7 Mpps
Driver mlx5 at 50Gbit/s.

---

Jesper Dangaard Brouer (3):
      Revert "icmp: avoid allocating large struct on stack"
      net: reduce cycles spend on ICMP replies that gets rate limited
      net: for rate-limited ICMP replies save one atomic operation

 net/ipv4/icmp.c |  125 +++++++++++++++++++++++++++++++++----------------------
 net/ipv6/icmp.c |   68 +++++++++++++++++++++---------
 2 files changed, 123 insertions(+), 70 deletions(-)

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